Devices that have removable battery packs, such as laptop computers, personal audio and video players, etc., most often have two power input jacks. The first power-input port is obvious . . . it is where the connector from the external wall adapter, AC/DC power-conversion adapter, DC/DC automotive cigarette-lighter adapter, external battery charger, etc., is plugged in.
The second power-input port is not so obvious . . . it is where a removable battery pack connects to its associated host device. Usually, this is a power (or mixed-signal power and data) connector hidden in a battery bay, or expressed as a cord and connector inside a battery compartment, such as is found in some cordless phones. The connector between a battery pack and its associated host device may simply be a group of spring contacts and a mating set of contact pads. This second power port is not used for external power (a host's removable battery power source is usually not classified as “external” power). The battery power port is so unrecognized that even supplemental external “extended run-time” battery packs, as are available from companies like Portable Energy Products, Inc. (Scotts Valley, Calif.), connect to the same traditional power jack to which the external power supply does.
The connector assembly herein exploits this un-utilized battery-to-host interface in a number of ways. As will be seen, a battery pack's power port is, in many ways, a far more logical power interface than the traditional power-input jack. By using a flexible and scaleable connector that is small enough to be enclosed within a battery pack housing, and providing sufficient connector contacts to handle power, the usefulness of external power devices and the battery pack itself can be enhanced.
Also, “smart” battery packs support connectors that are mixed signal, i.e., both power and data, therefore external power devices can data communicate with host devices and smart batteries, often facilitating device configuration, operation and power monitoring.
Some of the reasons why the battery-contact interface isn't used are that it's often inaccessible. In laptop computers, for example, the battery-to-host-device connector is often buried deep in a battery bay. The connector assembly described in this document is built into the battery pack itself, at a location where easy access to a connector is available. Where appropriate, conductors from a non-removable battery are routed to an accessible location on the host device. Even when the location of the connector assembly is remote from the battery pack, the interface addressed is that between the battery pack and its associated connector on the host device.
Another reason for the lack of attention to the battery's power connector is that the type of connector used between a battery and its host device is not usually of the design and style that would easily lend itself to being attached to the end of a power cord. A good example of how awkward such battery access connectors can be is the “empty” battery housing with power cord that is popular with camcorders. The camcorder's “faux” battery pack shell snaps into the normal battery pack mount, and there is usually a hardwired cord to a power-conversion adapter. This makes for a considerable amount of bulky goods to transport. That is the case with cellular phones, as well, with “empty” battery housings that plug into an automotive cigarette lighter, or a battery pack with an integrated charger. These are often bulkier than the battery pack they replace and, almost always, one must have a unique assembly—complete with cords—dedicated to a specific make or model of cellular phone.
The connector assemblies shown in the various figures, and described herein, are designed to be of the look and style normally associated with power and or data cords. Barrel-style connectors, and segmented-pin-types are common connector styles. By defining new barrel connectors that feature segmented contacts, or using segmented pin connectors in wiring schemes that create new connectivity paths, hitherto unknown ways of dealing with safety through power sub-system configurations are achieved. No bulky external add-ons are used. Instead, miniaturized connectors that can be embedded within an existing battery pack define new ways of powering battery-powered devices.
The battery packs discussed here are not empty battery enclosures, with only passthrough wiring. The original battery cells, circuit boards, fuses, etc., are all present and the connectors shown herein provide means to have a battery pack operate normally when the plugs are removed (or replaced).
Battery Pack Removal
Another reason a battery port connector is not used is that to access this unexploited power port would require removing the battery pack, which would result in the loss of available battery power. Some host devices require that a battery pack be present, as the battery may be serial-wired. Also, host devices are known that use the battery pack as a “bridge” battery that keeps CMOS, clocks, etc., functioning. Battery removal could negatively impact such devices. Removing a battery pack also results in even more bulky things to carry around, which hardly fits the travel needs of someone carrying a laptop or other mobile device.
A host device and its associated battery pack present a well-suited environment for a connector assembly that can, by the insertion or removal of its plug element, create or reconfigure circuits.
Battery packs or holders, with either primary cells or rechargeable cell clusters, are typically removable. So, if an interface apparatus is fitted into the confines of an existing battery pack, and the newly-created circuits achieved by doing so can be defined by contacts and conductors integrated into the battery pack itself, then the use of host devices is dramatically enhanced. Reconfiguring the battery pack does not change the existing contacts on the exterior of the battery enclosure, nor the contacts at the device-side of the as-manufactured battery-to-device I/O port. Consumers can simply acquire such an upgraded removable battery pack, and install the reconfigured one. Manufacturers of host devices will be able to offer an accessory product that enhances the usefulness and functionality of their host devices, without having to modify existing host devices already in consumers' hands.
Because batteries do wear out, consumers will—sooner or later—require a replacement battery pack. For example, today's Lithium-Ion battery cells claim about 500 charge/discharge cycles. In reality, the average battery user can expect only about 300. That usually equates to the battery's storage capacity starting to show signs of decreased run time in approximately 1-1.5 years. The user's awareness of decreased capacity may happen even sooner, especially with cellular phone battery packs. Reduced talk time or wait time is often noticed quickly by a cellular phone user. But, whatever the application, battery-powered device users inevitably are required to replace a worn-out battery.
By embedding connectors in the battery pack, no circuits are created within the host devices. This is useful because battery packs are virtually always removable and replaceable. Instead of having to pre-plan and design-in new power and data paths into a host device, the replaceable battery pack contains these power and data paths. Simply replacing a battery pack upgrades any host device. By placing the technology in a fully-functional battery pack, it is not necessary to remove the battery pack during connector operations . . . instead, keeping the battery pack in its host device, where it belongs, is essential.
Devices that use external power-conversion adapters invariably are designed to always charge the device's removable battery pack every time the external adapter is used. It seems logical that keeping the battery capacity at 100% is a sound practice. However, certain rechargeable battery chemistries don't offer the charge/recharge cycle life that was available with “older” battery technologies. Lithium-Ion (Li-Ion) batteries, for example, can last for only 300 cycles, and sometimes even less than that. In average use, an Li-Ion battery can have a useful life (full run-time, as a function of capacity) of less than a year, and nine months isn't uncommon. Constantly “topping-off” a Lithium-Ion battery only degrades useful battery life.
Being able to elect when to charge the battery, independent of powering the host device, would prolong the life of expensive batteries. By delivering power from external power adapters and chargers through connectors at a newly-defined battery power port, a user need only perform a simple act, such as rotating a connector to select a battery-charge mode, a host-power only mode, or both.
Battery Charging Risks
Battery charging is a destructive process in other ways than repeated unnecessary battery charging sessions. Low-impedance batteries, such as Lithium-Ion, generate heat during the charging process. This is especially true if a cell-voltage imbalance occurs for, as resistance increases, the entire battery pack can overheat. Lithium-ion cells have a reputation for volatility. For example, an article in the Apr. 2, 1998, edition of The Wall Street Journal reported on the potentials of fire, smoke and possible explosion of Li-Ion batteries on commercial aircraft (Andy Pasztor, “Is Recharging Laptop in Flight a Safety Risk?”, The Wall Street Journal, Apr. 2, 1998, pp. B1, B12).
To be able to easily disengage a volatile battery cell cluster from its integrated, hardwired battery charging circuit has obvious safety benefits. Several of the modalities of the connector assemblies discussed herein lend themselves to a simple battery bypass circuit within the battery pack, so that a host device can be powered from an external power source such as an aircraft seat-power system, without charging the battery. This function is achievable by simply replacing an existing battery pack with one that incorporates the connector assembly. This is a cost-effective, simple and convenient solution to an important safety concern. Because the connector assembly is a modification to an existing battery pack, and battery products already have a well-established and wide distribution network, availability of this safety device is widespread. No entirely new devices are required to be designed and fabricated, since the connector assembly is essentially an upgrade modification.
Power-Conversion Adapters
Battery flammability and explosive volatility are related to inappropriate power devices upstream of the battery pack. Connecting a power-conversion adapter that has an output voltage not matched to the input voltage of a host device is an easy mistake to make. Laptop computer input voltages, for example, can range from 7.2VDC, to 24VDC. Within that voltage range are a significant number of AC/DC and DC/DC adapters that are power-connector-fit compatible, but which output incompatible voltages. A count of notebook computer power-conversion adapters available from one mail order company numbered over 250 discrete products (iGo, Reno, Nev., www.iGoCorp.com). The probability of a voltage mismatch indicates a serious concern.
Compared to the multiplicity of vast and diverse input voltages battery-powered host devices require, input voltages at battery power ports are not only limited, but more flexible. Since battery output voltages are a function of an individual cell voltage, multiplied by the number of cells wired in series or parallel, there are a limited number of output voltages for battery packs. For example, Lithium-Ion cylindrical cells are manufactured at only 3.6-volts (some are 4.2-volt cells). Thus, virtually every Li-Ion battery pack made outputs either 10.8, or 14.4 volts (with some relatively rare 12.6-volt cell clusters). If an external power-conversion adapter was designed to provide power to a notebook computer host device through the host device's battery port, it is possible that only two output voltages would be required, since the external adapter would electrically “look” to a host device as a battery pack. This adds value to a connector assembly that can eliminate the problem of there being some 42 different types of existing laptop power connectors.
Furthermore, battery pack output voltages vary as a function of charge state. A fully charged battery rated at 10.8-volts actually outputs voltages in a range from about 10 volts, through 14.0-volts (with transient voltages up to 16 volts), depending on the battery's state of charge or discharge. This same host device may be able to accept input voltages at its usual external power-adapter input port within a narrow voltage range of +/−1-volt. Thus, host devices have a far greater tolerance for potential voltage mismatches at their battery power ports, as compared to at the traditional power jack. By providing a power connector that uses the battery's power port, the number of external power devices is significantly reduced, and the overall risk of damaging a host device by a voltage mismatch is minimized.
The heat dissipation from charging a Lithium-Ion battery pack is compounded by the heat being generated by advanced high-speed CPUs. With computer processors running so hot in portable devices that heat sinks, fans, heat pipes, etc., are required, the additional heat from charging a battery only intensifies the thermal issues.
The connector assembly described herein, by disengaging battery charging, extends the life of a host device's components and circuits that otherwise may be compromised or stressed by extended hours of exposure to heat. This is especially valid for host devices like laptop computers, since a number of these products are not used for travel, but instead spend almost all of their useful lives permanently plugged into the AC wall outlet in a home or office, serving as a desktop substitute. In such device applications, the need to repeatedly charge the laptop's battery has no practicality. By using a connector assembly that can be selectively put into a mode of battery charging only when necessary, the working life expectancy of these host devices can be extended by eliminating unnecessary overheating.
Energy Conservation
There's a less obvious reason to not charge batteries on commercial aircraft. Some commercial passenger aircraft provide power systems with power outlets at the passenger seat. The head-end aircraft power source is a generator, so the total amount of energy to power all of the aircraft's electrical system is limited. The Airbus A319, for example, has only sufficient generator capacity to provide seat power for less than 40 passengers' laptop computers (Airbus Service Information Letter (SIL), dated 8 Jan. 1999). A laptop computer being powered from an external power-conversion adapter uses 2040% of the external power to charge its battery pack, which translates to about 15-30 Watts. Generating sufficient power to charge 200+laptop batteries puts a considerable drain on the aircraft's electrical system.
Disabling battery charging by employing a connector assembly described herein is a cost-effective means of lowering an airline's operating costs, by minimizing the total load schedule of the cabin power grid. The airline saves the cost of the fuel required to operate the generator at a higher power capacity.
Airline operators have policies and in-flight rules that prohibit the types of passenger electronic devices that can legally operate on the plane. The use of RF devices, such as cellular phones, and radio-controlled toys, is banned on every commercial aircraft. Passengers may be confused on aircraft operated by American Airlines, for example, since selected passenger seats have power systems for laptop use. This airline's seat power outlet is a standard automotive cigarette-lighter port. An unsuspecting passenger, mistakenly assuming that the cigarette-lighter port was for cellular phones, could easily plug in and turn on a cell phone.
Because there are a number of modalities to the connector assembly described in this document, airlines can elect to use a specific connector style, shape or wiring scheme that is reserved for passenger seat-power. By limiting the use of a receptacle to battery packs for laptops, and not allowing the connector to be used in cellular phone battery packs, for example, an airline can control the types of passenger devices it allows to be connected to its cabin power system.
Battery-Only-Powered Devices
There is also a variety of battery-powered devices that does not have an external power-supply power input jack. Cordless power tools, flashlights, and other devices meant to run strictly on removable and/or externally rechargeable batteries may not have been manufactured with an alternative means of power. If the battery of a cordless drill goes dead, for example, the only recourse is usually to remove the battery and recharge it in its external charger. This is frustrating to anyone who has had to stop in the middle of a project to wait for a battery to recharge.
By integrating a new connector assembly, such as the ones shown in the figures and text herein, circuits can be created that use a host device's battery-power-port interface as a power connector through which power can be delivered from an external power source. A user can elect, when a power outlet is available, to operate devices such as battery-powered drills, saws, etc., from external power, simply by attaching a compliant external power adapter into the connector interface on an exposed face of the battery pack. With some modalities of the connector assembly that is the invention, an external charger can be connected as well, allowing simultaneous equipment use and battery charging in products that hitherto did not have these capabilities.
Devices with holders for individual battery cells fall into this same category of not having an external power port. If the device does have an external port, it is not wired to provide simultaneous battery charging. Not being able to charge replaceable battery cells in a battery holder that is inside the host device lessens the usefulness of rechargeable alkalines, for example.
It is more convenient to leave individually replaceable battery cells in their battery holder while charging, and a number of the modalities of the connector assembly discussed herein allow for that. The added convenience of being able to operate a host device instead of draining its rechargeable alkalines (these battery types typically can only be recharged 10-20 times, then must be discarded), reduces operating costs. The use of the connector assembly saves time, since the user doesn't have to take the time to remove each individual cell and place it in a special charger.